I think the difference is it's a little easier to control other forms of "screen time". That other stuff is pure entertainment and they don't have the addictive aspect of a feed.
I think maybe it's because you can't win at Facebook. All the other forms of entertainment give you a sense of satisfaction on completion. Facebook is the complete opposite. It doesn't end and you can't really win at it. That's great from a commercial perspective but utterly unfulfilling for the user.
I dunno man, some games are really fucking addictive these days. Especially with some of the abusive gambling mechanics.
I would argue staunchly, that Fortnite (PS4 online version) is every bit as "addictive" as a FB feed. Ultimately, all they provide are shots of dopamine.